1. Field
The exemplary embodiments relate to methods and apparatuses for adjusting an aperture in an optical system.
2. Description of the Related Art
A technique of adjusting and controlling a transmissivity of light is widely used for an iris or shutter in image acquisition devices, or is used to drive individual pixels in image display devices.
A variable iris generally used in existing optical systems mainly utilizes a method of manipulating several metal blades, wherein a mechanical motion, a frictional force, and the use of a moving mechanical element limit miniaturization.
Recently, variable irises have been proposed using a microelectrofluidic method using an electrowetting technique. The electrowetting technique, which is a technique of controlling a contact angle of a polar liquid, has been largely used in various fields, such as lab-on-a-chip, a liquid lens, a display, and the like, with characteristics of a quick response speed and low power consumption.
A variable iris using a microelectrofluidic method includes an electrode, upper and lower channels through which a fluid flows, and polar and non-polar fluids disposed in the upper and lower channels. In response to a voltage being applied between an electrode coated with a dielectric and the polar-fluid, an electromechanical force works on a three-phase contact line (TCL) between a fluid interface and the electrode, and results in changing, a contact angle. Accordingly, a Laplace pressure difference in the upper and lower channels is caused to make the polar fluid in the lower channel flow inwards (towards a center) or outwards (towards a circumference), and thus, the size of the aperture can be varied.
Although the variable iris using a microelectrofluidic method has a high aperture ratio, a low driving voltage, and a quick opening/closing speed, accuracy is necessary. As a result, a driving force at a very precise level is applied to control an aperture size, and an initial droplet amount may be accurately controlled in order to accurately define an aperture location in an initial iris state, and the like.